Generally, an image forming apparatus such as a printer, a copying machine, and a facsimile irradiates a charged photosensitive drum with image information using an exposure module, generates an electrostatic latent image, and uses a toner to develop the electrostatic latent image. Then, the image forming apparatus may transfer and settle a toner image on a printing medium and form an image on the printing medium.
As the exposure module used in the above case, a laser scanning unit (LSU) that uses laser to scan a laser beam in a scanning direction has been widely used.
In recent years, research on a light emitting diode (LED) print head (LPH), in which a plurality of LEDs are arranged in a scanning direction and the plurality of LEDs sequentially generate light, has been carried out to reduce the size of the exposure module.